1. Field of the Invention
The present application relates generally to Customer Premises Equipment (CPE) such as telephones and, more particularly, to an improved method and apparatus for receiving digital data from a Local Switching Office (LSO) while the CPE is communicating with another CPE in an off-hook state.
2. Description of Related Art
The telecommunications industry has developed and implemented a number of innovations related to enhancing the functionality of Customer Premises Equipment (CPE). The industry has, for example, implemented a system known generally as Call Waiting wherein a first party, while communicating off-hook with a second party, may be informed that a third party wishes to communicate with the first party. In general, the Call Waiting feature is implemented by having the LSO send an audible call waiting tone to the first party CPE. The user of the first party CPE, after hearing the call waiting tone, may switch back and forth between the second and third party by xe2x80x9cflashingxe2x80x9d his CPE.
The telecommunications industry has also developed a system known generally as Caller Identification (CID) wherein the LSO transmits digital data to the first party CPE which then displays information regarding the identity of the calling party based on the digital data. The LSO generally transmits the digital data to the CPE using FSK modulation.
A xe2x80x9cType 2xe2x80x9d CID system operates only while the first party CPE is on-hook. The Type 1 CID system, in other words, operates only when the first party CPE is not transmitting any first party signals to the LSO that would interfere with the LSO""s transmission of the digital data. The Type 1 CID system also assumes that the first party is not listening to the CPE and will not hear the digital data transmitted by the LSO.
A xe2x80x9cType 2xe2x80x9d CID system, however, permits off-hook signaling. Accordingly, the LSO may send the digital data corresponding to a third party while the first party CPE is communicating off-hook, via the LSO, with a second party. The general operation of a conventional Type 2 CID system is described in U.S. Pat. No. 5,263,084 entitled xe2x80x9cSpontaneous Caller Identification With Call-Waitingxe2x80x9d by inventors Guy J. Chaput, et al., issued Nov. 16, 1993, and assigned to Northern Telecom Limited (hereafter the ""084 patent). As described in the ""084 patent, Type 2 CID generally requires that the LSO transmit a special call waiting tone called a CPE Alerting Signal (CAS). The CAS is a dual-tone signal that is nominally 80 milliseconds in duration. The CAS informs the first party CPE that a third party call is available and that the LSO is prepared to transmit digital data regarding the third party. If the first party CPE is a Type 2 CPE that is capable of off-hook signaling, it responds to the CAS with an acknowledgment signal (ACK). The ACK signal informs the LSO that the first party CPE is capable of receiving the digital data. This CAS-ACK xe2x80x9chandshakexe2x80x9d prevents the LSO from transmitting the digital data to a CPE which is not capable of receiving and acting upon the digital data and thereby relieves the user from having to hear the generally annoying, modem-like noises of the digital data.
The CPE of the ""084 patent mutes its handset 14 via switches 17, 18 after detecting the CAS and then receives the CID data from the LSO. This approach suffers from certain disadvantages. In particular, a CPE made according to the ""084 patent completely mutes the acoustic transducers by disconnecting them with switches 17, 18. Muting the loudspeaker, however, unnecessarily imposes a potentially uncomfortable silence on the user while the first party CPE is receiving the digital data. If the first party CPE is sending a locally stored signal/message to the loudspeaker at the time of the CAS being received then muting the loudspeaker will unnecessarily interfere with this operation. In addition, by disconnecting and thereby completely disabling the microphone, a CPE made according to the ""084 patent cannot perform any ongoing functions on the input signal from the microphone. Examples of such functions include the update of acoustic echo cancellers or local voice recording.
Accordingly, there is a need for a method and apparatus for a first party CPE to receive digital data from the LSO while communicating in an off-hook state with a second party that does not impose an uncomfortable silence on the first party listener and does not preclude functionality such as recording first party voice signals while receiving the digital data from the LSO.
The present invention relates to a method of receiving digital data from a Local Switching Office (LSO) on first party equipment that is communicating, in an off-hook state, via the LSO, with second party equipment, the first party equipment having a line interface for receiving signals from and transmitting signals to a telephone line connected to the LSO and an acoustic interface for receiving signals from a microphone and for transmitting signals to a loudspeaker. In a preferred embodiment, the method comprises the steps of the first party equipment receiving an alert signal from the LSO via the line interface while communicating, in an off-hook state, with the second party equipment, the alert signal indicating that the LSO is prepared to send the digital data; the first party equipment temporarily preventing a first party signal from being transmitted to the line interface after the alert signal has been received; the first party equipment sending an acknowledgment signal to the LSO in response to the alert signal via the line interface indicating that the first party equipment is capable of receiving the digital data; the first party equipment transmitting a predetermined local signal to the loudspeaker via the acoustic interface while receiving the digital data via the line interface to relieve the first party from having to hear the actual reception of the digital data or from having to listen to a silent loudspeaker; the first party equipment, after receiving the digital data via the line interface, restoring the first party signal to the line interface and no longer transmitting the predetermined local signal to the loudspeaker via the acoustic interface; and the first party equipment performing a function based on the digital data.
In a preferred embodiment, the digital data comprises caller ID information as transmitted to a Type 2 telephone capable of receiving such information and the local signal comprises a discrete comfort signal of predetermined nature. The comfort signal may, if desired, audibly indicate that the digital data is being received. Finally, in an alternative embodiment, the local signal comprises an intermediate portion of locally recorded message which was being provided to the loudspeaker before receipt of the alert signal.